Conservation of the prion properties of Ure2p through evolution

The yeast inheritable [URE3] element corresponds to a prion form of the nitrogen catabolism regulator Ure2p. We have isolated several orthologous URE2 genes in different yeast species: Saccharomyces paradoxus, S. uvarum, Kluyveromyces lactis, Candida albicans, and Schizosaccharomyces pombe. We show here by in silico analysis that the GST-like functional domain and the prion domain of the Ure2 proteins have diverged separately, the functional domain being more conserved through the evolution. The more extreme situation is found in the two S. pombe genes, in which the prion domain is absent. The functional analysis demonstrates that all the homologous genes except for the two S. pombe genes are able to complement the URE2 gene deletion in a S. cerevisiae strain. We show that in the two most closely related yeast species to S. cerevisiae, i.e., S. paradoxus and S. uvarum, the prion domains of the proteins have retained the capability to induce [URE3] in a S. cerevisiae strain. However, only the S. uvarum full-length Ure2p is able to behave as a prion. We also show that the prion inactivation mechanisms can be cross-transmitted between the S. cerevisiae and S. uvarum prions.     

Novel cationic amphiphilic 1,4-dihydropyridine derivatives for DNA delivery

In order to find new efficient and safe agents for gene delivery, we have designed and synthesized nine novel single- and double-charged amphiphiles on the base of 1,4-dihydropyridine (1,4-DHP) ring. Some biophysical properties of the amphiphilic dihydropyridines and their complexes with DNA were examined. We investigated the transfer of beta-galactosidase gene into fibroblasts (CV1-P) and retinal pigment epithelial (D 4O7) cell lines in vitro. The structure-property relationships of the compounds were investigated in various ways. The net surface charges of 1,4-DHP liposomes were highly positive (25-49 mV). The double-charged compounds condensed DNA more efficiently than single-charged and the condensation increases with the increasing +/- charge ratio between the carrier and DNA. Double-charged compounds showed also buffering properties at endosomal pH and these compounds were more efficient in transfecting the cells, but transfection efficiency of amphiphiles was cell type-dependent. The length of alkyl chains in double-charged compounds affected the transfection efficacy. The most active amphiphile (compound VI) was double-charged and had two C(12) alkyl chains. At optimal charge ratio (+/- 4), it was 2.5 times more effective than PEI 25 and 10 times better than DOTAP, known efficient polymeric and liposomal transfection agents. Formulation of amphiphiles with DOPE did not change their activities. Our data demonstrate some important effects of amphiphile structure on biophysics and activity. The data also suggest that cationic amphiphilic 1,4-DHP derivatives may find use as DNA delivery system.     

Microphytobenthos production in the Gulf of Fos, French Mediterranean coast

Microphytobenthic oxygen production was studied in the Gulf of Fos (French Mediterranean coast) during 1991/1992 using transparent and dark benthic chambers. Nine stations were chosen in depths ranging from 0.5 to 13 m, which represents more than 60% of bottoms in the Gulf. Positive net microphytobenthic oxygen production was seasonally detected down to 13 m; the maximum value attained was 60 mg O₂ m⁻² h⁻¹ (0.7–0.8 g O₂ m⁻² d⁻¹) in sediments at 0.5 m depth during spring and winter. Respiration rates were maximum in the sediments located at the mussel farm (5 m), in the center of the Gulf, with 135 mg O₂ m⁻² h⁻¹ in spring (3.2 g O₂ m⁻² d⁻¹); in the other locations, it ranged from 3.3 to 58.2 mg O₂ m⁻² h⁻¹ (0.08–1.4 g O₂ m⁻² d⁻¹). Compared to phytoplankton, microphytobenthos production was higher only in the bottoms < 1 m depth. In deeper bottom waters, phytoplankton production could be absent due to light limitation, while microphytobenthos was still productive. Phytoplankton production m⁻² was generally higher than microphytobenthic production. Microphytobenthic biomass, higher than phytoplanktonic, varied from 27 to 379 mg Chl a m⁻², the maximum in the mussel farm sediments, with the minimum in sandy shallow bottoms. Pigment analysis showed that microphytobenthos consisted mainly of diatoms (Chl c and fucoxanthin) but other algal groups containing Chl b could become seasonally important. A Principal Component Analysis suggested that the main statistical factors explaining the distribution of our observations may be interpreted in terms of enrichment in phaeopigments and light; the role of Chl a appearing paradoxically as secondary in benthic production rates. Phaeopigments are mainly constituted by phaeophorbides, which indicate grazing processes. The influence of the mussel farm on the oxygen balance is noticeable in the whole Gulf.     

Hormonal changes in satisfied and dissatisfied shift workers across a shift cycle.

Although the literature claims that shift work is harmful, it overlooks the fact that that many shift workers are satisfied and stay healthy. There is little knowledge of the biological mechanisms mediating the differences in susceptibility. The present study compared satisfied and dissatisfied shift workers with respect to major anabolic and catabolic hormones. Forty-two male shift workers, with an extremely rapidly rotating shift schedule, were divided into two groups according to their ratings of satisfaction with their work hours. Morning blood samples were taken during the first and last morning shift in the shift cycle. Serum was analyzed with respect to testosterone, cortisol, and prolactin. Dissatisfied shift workers had lower morning testosterone than satisfied ones, but they did not significantly differ with respect to cortisol or prolactin. Low testosterone levels were, in addition, associated with a greater sleep need, disturbed sleep/wakefulness, and an increased need for recovery after the work period, the latter being the best predictor of testosterone levels. The only change across the shift cycle concerned a significant decrease of morning cortisol at the end of the shift cycle. High morning cortisol was related to having a morning personality and fewer sleep problems before the morning shift. Dissatisfaction with the shift system seems related to lower testosterone levels, which in turn are related to disturbed sleep/wakefulness and increased need for sleep and recovery. Furthermore, morning cortisol was reduced across a shift cycle. It is suggested that reduced testosterone levels may be part of a mechanism of shift work maladjustment.     

A stretch of residues within the protease-resistant core is not necessary for prion structure and infectivity

Mapping out regions of PrP influencing prion conversion remains a challenging issue complicated by the lack of prion structure. The portion of PrP associated with infectivity contains the α-helical domain of the correctly folded protein and turns into a β-sheet-rich insoluble core in prions. Deletions performed so far inside this segment essentially prevented the conversion. Recently we found that deletion of the last C-terminal residues of the helix H2 was fully compatible with prion conversion in the RK13-ovPrP cell culture model, using 3 different infecting strains. This was in agreement with preservation of the overall PrP^C structure even after removal of up to one-third of this helix. Prions with internal deletion were infectious for cells and mice expressing the wild-type PrP and they retained prion strain-specific characteristics. We thus identified a piece of the prion domain that is neither necessary for the conformational transition of PrP^C nor for the formation of a stable prion structure.     

Reduction of surface sulphur upon microbial devulcanization of rubber materials

Thiobacillus ferrooxidans, T. thioparus, Acidianus brierleyi and TH2 Lund, an archaeal isolate, were tested for sulphur oxidising capacity on ground rubber from spent car tyres. T. ferrooxidans converted 8 % (w/w) of the sulphur in cryoground spent rubber to sulphate in 20 days. Desulphurization of fresh made natural rubber was studied with scanning electron microscope with energy-dispersive x-ray spectrometer and electron spectroscopy for chemical analysis. The average depletion of sulphur on the treated surface was 24 % compared to the bulk region. Oxidised sulphur species were detected on the surface after microbial treatment. © Rapid Science Ltd. 1998     

Chlorogenic Acid Metabolism: The Evolution and Roles in Plant Response to Abiotic Stress

During the evolution, plants acquired the ability to synthesize different phenylpropanoid compounds like chlorogenic acid (CGA), which plays vital roles in resistance mechanisms to abiotic stresses. These environmental factors, including heavy metal, cold, heat, ultraviolet (UV) light, drought, and salinity affect the plant physiological processes, resulting in massive losses of agriculture production. As plants evolve from green algae to bryophytes, ferns, gymnosperms and angiosperms, phenylpropanoids are produced and accumulated in different tissues, giving the plant the capacity to counteract the harmful effects of the adverse environments. Studies have been performed on the metabolic evolution of rosmarinic acid, flavonoids and lignin, showing that the biosynthesis of phenylpropanoids begins in green algae until the emersion of genes found in angiosperms; however, the evolution of the CGA pathway has not yet been reviewed. We hypothesize that CGA could also be synthesized from algae to angiosperms. In the present review, the evolutionary analysis of CGA pathway and the function of this compound in plant tolerance to abiotic stresses are summarized. Bioinformatics analyzes were carried out on CGA-related genes across 37 plant species and revealed that the metabolic pathway starts in algae and gradually increases until it becomes complete in angiosperms. The key genes exhibited different expression patterns in stress and plant tissues. Interestingly, some genes accumulated rapidly during evolution and were more sensitive to environmental stresses, while others appeared only later in angiosperms. Further studies are needed to better understand the evolution of the CGA metabolic pathway in plants under environmentally stressed conditions.     

Sheep and goat BSE propagate more efficiently than cattle BSE in human PrP transgenic mice

A new variant of Creutzfeldt Jacob Disease (vCJD) was identified in humans and linked to the consumption of Bovine Spongiform Encephalopathy (BSE)-infected meat products. Recycling of ruminant tissue in meat and bone meal (MBM) has been proposed as origin of the BSE epidemic. During this epidemic, sheep and goats have been exposed to BSE-contaminated MBM. It is well known that sheep can be experimentally infected with BSE and two field BSE-like cases have been reported in goats. In this work we evaluated the human susceptibility to small ruminants-passaged BSE prions by inoculating two different transgenic mouse lines expressing the methionine (Met) allele of human PrP at codon 129 (tg650 and tg340) with several sheep and goat BSE isolates and compared their transmission characteristics with those of cattle BSE. While the molecular and neuropathological transmission features were undistinguishable and similar to those obtained after transmission of vCJD in both transgenic mouse lines, sheep and goat BSE isolates showed higher transmission efficiency on serial passaging compared to cattle BSE. We found that this higher transmission efficiency was strongly influenced by the ovine PrP sequence, rather than by other host species-specific factors. Although extrapolation of results from prion transmission studies by using transgenic mice has to be done very carefully, especially when human susceptibility to prions is analyzed, our results clearly indicate that Met129 homozygous individuals might be susceptible to a sheep or goat BSE agent at a higher degree than to cattle BSE, and that these agents might transmit with molecular and neuropathological properties indistinguishable from those of vCJD. Our results suggest that the possibility of a small ruminant BSE prion as vCJD causal agent could not be ruled out, and that the risk for humans of a potential goat and/or sheep BSE agent should not be underestimated.     

Role of vascular endothelial growth factor in the communication between human osteoprogenitors and endothelial cells

Proper bone remodeling requires an active process of angiogenesis which in turn supplies the necessary growth factors and stem cells. This tissue cooperation suggests a cross‐talk between osteoblasts and endothelial cells. This work aims to identify the role of paracrine communication through vascular endothelial growth factor (VEGF) in co‐culture between osteoblastic and endothelial cells. Through a well defined direct contact co‐culture model between human osteoprogenitors (HOPs) and human umbilical vein endothelial cells (HUVECs), we observed that HUVECs were able to migrate along HOPs, inducing the formation of specific tubular‐like structures. VEGF₁₆₅ gene expression was detected in the HOPs, was up‐regulated in the co‐cultured HOPs and both Flt‐1 and KDR gene expression increased in co‐cultured HUVECs. However, the cell rearrangement observed in co‐culture was promoted by a combination of soluble chemoattractive factors and not by VEGF₁₆₅ alone. Despite having no observable effect on endothelial cell tubular‐like formation, VEGF appeared to have a crucial role in osteoblastic differentiation since the inhibition of its receptors reduced the co‐culture‐stimulated osteoblastic phenotype. This co‐culture system appears to enhance both primary angiogenesis events and osteoblastic differentiation, thus allowing for the development of new strategies in vascularized bone tissue engineering. J. Cell. Biochem. 106: 390–398, 2009. © 2009 Wiley‐Liss, Inc.     

The structure of the O-chain of the lipopolysaccharide of a prototypal diarrheagenic strain of Hafnia alvei that has characteristics of a new species under the genus Escherichia.

The structure of the O-polysaccharide of the lipopolysaccharide from a diarrheal strain isolated in Bangladesh was studied with sugar, and methylation analysis, NMR spectroscopy, mass spectrometry and partial acid hydrolysis. The strain was first designated as Hafnia alvei, but later found to be a possible new species in the genus Escherichia. Two different polysaccharides were detected, a major and a minor one. The structure of the major polysaccharide is given below, while the structure of the minor one was not investigated. The structure of the repeating unit was established as The structure does not resemble any of the previously investigated lipopolysaccharide O-chains from Escherichia coli or H. alvei, but could fit in either group based on types of sugar residues and acidity. Phenotypic microbiological studies cannot definitely assign it to either species of the two genera. Genetic hybridization studies indicate that the Bangladeshi isolates may require a new species designation under the genus Escherichia.